1. Field of the Invention
The present invention relates to drivers and, more particularly, to a driver with a bulk switching MOS power transistor.
2. Description of the Related Art
A MOS transistor is a well-known circuit device that controllably varies the current that flows between a source region and a drain region. A MOS power transistor is a larger MOS transistor that is capable of handling much larger magnitudes of current. A driver is another well-known circuit device that utilizes a PMOS power transistor and an NMOS power transistor.
The PMOS transistor has a source connected to a voltage source, and a drain connected to an output node. In addition, the PMOS transistor has a gate, and an n-bulk that is connected to the voltage source. The NMOS transistor has a source connected to ground, and a drain connected to the output node. Further, the NMOS transistor has a gate, and a p-bulk that is connected to ground.
In operation, when an input signal transitions from a logic low to a logic high, the PMOS transistor turns off and the NMOS transistor turns on. As a result, the NMOS transistor pulls the output node to ground. On the other hand, when the input signal transitions from a logic high to a logic low, the NMOS transistor turns off and the PMOS transistor turns on. As a result, the PMOS transistor pulls the output node up to approximately the voltage source.
One of the advantages of the above-described driver is that only one transistor is on when the input logic state is either a logic high or a logic low. To minimize leakage current when the PMOS and NMOS transistors are turned off, the n-bulk and p-bulk, respectively, are held at the voltage source and ground, respectively.